1. Field of the Invention
The present invention relates to a navigation apparatus for use with a vehicle such as an automobile and to a matching method for navigation.
2. Description of the Related Art
Recently, in many companies, laboratories, and the like, a navigation system for use with a vehicle, for example, an automobile, has been actively developed. New and improved products of the navigation system have been marketed one after another. Generally, a navigation apparatus is carried in a vehicle, and is made up of a microcomputer, various types of sensors, a display, and the like. It employs a so-called conjecture navigation method for its navigation. The sensors collect necessary data, then the microcomputer properly processes the collected data to obtain the present position of the vehicle. The display displays the present position or a locus representing the progressive path of the vehicle on a displayed map. The driver can be aware of the present position, and determine a route to a destination, or be kept informed of the route along which the vehicle is going.
The navigation apparatus uses the present position data as calculated by using various types of data collected by the sensors, such as speed, direction, and running time, and the prestored exact position data (absolute position data or surveyed data) of specific positions, which overlay a map being displayed on the screen of the apparatus. As the vehicle moves, the matching of the various data with the surveyed data is lost and the difference between them accumuatively increases. Some measure must be taken to deal with this problem. This measure exists and is called a map matching technique. So far as we know, there is no map matching technique able to satisfactorily solve the above problem.
In one approach for map matching, the surveyed data is collated probability-functionally with 3-dimensional map error, error involved in surveying specific positions, and errors due to data being displayed as combinations of curves and approximated linear curves. This approach succeeds in obtaining an exact matching under simple and typical load conditions, but as a satisfactory matching technique under complicated road conditions, however, it requires many intricate processes. Further, size reduction of navigation apparatuses based on the above approach is very difficult, leading to cost increases.